SOMERVILLE — Faced with unraveling what had been described as a “wacky” tale, a jury today handed down a split verdict to an Irvington police officer for his alleged role in the robbery and beating of a teenage girl in a Raritan parking lot in October 2011.

Officer Herne Lacoste was found guilty of kidnapping, aggravated assault, hindering apprehension and official misconduct. He was found not guilty of robbery and three weapons offenses.

Dressed in a black suit, Lacoste was handcuffed behind his back after Superior Court Judge Robert Reed revoked his bail, and sent him to Somerset County jail to await sentencing.

His co-defendant in the trial, Shanikah Daniels, was found not guilty of robbery and possession of a firearm for an unlawful purpose, but she received a guilty verdict on the remaining five charges against her, including kidnapping and aggravated assault.

Daniels, who has not attended the trial lately for medical reasons, must report to court Tuesday morning, when her bail likely will be revoked and she’ll be sent to jail.

The jury had begun deliberations on Wednesday.

Prosecutors had argued that Lacoste, 41, of Plainfield, who was off-duty at the time, drove to a Raritan parking lot in the early morning hours of Oct. 16, 2011 with Daniels, Markeesa Coleman and the then-17-year-old girl.

Inside Lacoste’s Dodge Durango, Daniels allegedly used a gun belonging to Lacoste to rob the 17-year-old, stealing her cell phone, a bus ticket and a metro card, authorities said. After Daniels forced the victim out of the vehicle, she and Coleman beat the teenager while Lacoste looked on, authorities said.

Authorities said the stolen items were later recovered from Daniels’ apartment, and the gun was found inside Lacoste’s SUV.

Coleman accepted a plea agreement and testified against Lacoste and Daniels during the trial.

But Lacoste’s attorney, Dan S. Smith, argued during the trial that the gun had been stolen from his client’s home without his knowledge. In the parking lot, Lacoste had stepped out of the vehicle to urinate and was unaware of the robbery, Smith said. Lacoste had testified that he didn’t arrest the women during the altercation because it seemed like little more than a lover’s quarrel.

Following today’s verdict, Smith vowed to appeal the jury’s decision.

“We think obviously that the verdict, I think, is inconsistent with the evidence,” Smith said. “It’s an unfortunate set of circumstances…Hopefully, upon later review, he will receive a better outcome.”

After informing Daniels of the verdict by telephone, her attorney, James Wronko, said she was relieved to be found not guilty of the robbery offense, the most serious charge against her. But she is still facing prison time for other offenses, Wronko said.